What's Up, Tiger Lily? was Woody Allen's directorial debut. For this movie, he purchased a Japanese spy film and removed the sound track entirely. He then dubbed it over with a script of his own. In this new script, the "plot" most certainly has nothing to do with the original. (Think MST3K.)
The original film was called Kagi No Kag, which translates to Key of Keys. I can only guess at the original plot line; it was certainly something more along the lines of a James Bond film than what Allen turned it into: a bunch of gangsters fighting for possession of an egg salad recipe.
If you watch this movie, bear in mind that "plot" is in quotes. The idea behind the movie is far more brilliant and giggle-worthy than the reality turned out to be (in my humble opinion). On the other hand, I think it's definitely worth watching (if you have beer and don't hate Woody Allen). There are a few jokes that still strike me as funny, and it's been 10 years since I've seen it.